same curve, within the limits of experimental error. The study of radiations still less refrangible than those I have dwelt on appeared to me impracticable. To avoid confusion, I was obliged to adopt a very large scale for the ordinates; this is why I could not plot on the diagram the results of my former measurements of the more refrangible "N" rays (loc. cit.). These results give points situated on a branch of the curve, starting from the topmost point on the right, and rising almost vertically, with a feeble inclination, from bottom to top, and from right to left, and a slight convexity turned upwards.
Certain sources seem to emit N1 rays exclusively, or, at least, these rays predominate in the emission. This is the case with copper and silver wire, and with hard-drawn platinum wire. M. Bichat has observed that ethylic ether, when brought to the state of forced extension, by the process discovered by M. Berthelot, emits N1 rays. When this state of strain ceases, whether spontaneously or under the action of a slight blow, the emission of N1 rays immediately disappears.
